This invention is in the field of devices for the treatment of gastrointestinal disorders in human subjects.
At least 8% of the population has acid reflux, also known as gastroesophageal reflux disease (GERD), that is not controlled by the current treatment of choicexe2x80x94ion pump inhibitors that block acid production and other medications that affect contraction of the esophagus and gastroesophageal sphincter.
Some patients may experience transitory relaxations, typically of 5 to 35 seconds in duration (see Dent, J., Patterns of lower esophageal sphincter function associated with gastroesophageal reflux., Am. J. Med., Nov. 24, 1997; 103(5A): 29S-32S) of the gastroesophageal sphincter (GES, also known as the lower esophageal sphincter, or LES); this is the most common cause of reflux of acid and secretions from the stomach up into the lower esophagus. Armenian, B., Transitory relaxation of the esophageal inferior sphincter and gastroesophageal reflux, Rev Med. Suisse Romande, 1997; 117(10): 797-9. This reflux of secretions may cause pain and an increase in the risk of cancer of the esophagus even with use of medications.
Surgery is currently the only remaining choice for those who fail to respond to these medications. The results of surgery are often unsatisfactory. Other gastrointestinal disorders also involve disturbances of motility and sequential coordinated contraction from the esophagus to the lower bowel.
These disorders are frequently a result of a combination of lifestyle, excessive weight, and the effects of other medications (e.g. narcotics, antihypertensive, anti-inflammatories). The main problem is lack of sequential action of the gut musculature (e.g. loss of gastrocolic reflex due to diabetes, neuropathies, and medications such as narcotics, tranquilizers, and antidepressants).
Attempts to correct this problem have largely failed due to failure to consider coordinated sequential action of the GI tract.
Familoni et al. have shown in the dog model that the optimal frequency for stimulating stomach contraction is at four to five times the intrinsic rate of five cycles per minute. Familoni, B. O. et al., Electrical stimulation at a frequency higher than basal rate in human stomach, Dig. Dis. Sci., 1997 May; 42(5): 892-7. For the stomach, stimulation of one part will produce appropriate contraction of the whole stomach because the stomach acts as a syncytium (an integrated whole). While recent results of stimulation of the stomach in dogs have demonstrated efficacy in achieving motility (see Mintchev, M. P. et. al, Microprocessor-controlled movement of solid gastric content using sequential neural electrical stimulation, Gastroenterology, 2000 February; 118(2): 258-63), no implantable system has been envisioned to responsively stimulate the normal sequential action of more than a single segment of the gastrointestinal tract. To be successful in alleviating human gastrointestinal tract disorders, a treatment will often need to stimulate two or more segments of the gastrointestinal tract.
Numerous medications have been developed to suppress appetite or attempt to speed up the metabolism to treat obesity. None has been proven to be sufficiently specific or substantially free from side effects. Electrical stimulation of the brain to suppress or increase appetite has been shown in animals but the localization of the stimulation within the hypothalamus or other desired location is extremely difficult. There is ongoing work to determine if vagus nerve stimulation can successfully suppress appetite.
Fischell et al. in U.S. Pat. No. 6,016,449 describe a responsive programmable neurostimulator for the treatment of neurological events but does not describe the programming and techniques necessary for the treatment of gastrointestinal disorders.
Chen et al. in U.S. Pat. No. 5,690,691 describes a technique for pacing of the stomach and small intestine using phased stimulation with multiple electrodes, but does not consider using significant delays between stimulation of one organ and the next to emulate normal gastrointestinal tract function.
Familoni in U.S. Pat. No. 5,861,014 describes a system to sense and identify abnormal stomach electrical signals and to stimulate the stomach responsively to treat the detected gastric rhythm abnormalities. Familoni does not disclose the use of a system that involves the esophageal sphincter and would work for acid reflux, nor does he disclose the detecting of normal function and the use of the detected delays in normal gastrointestinal tract function to set the delays for triggering successive stimulation of gastrointestinal tract organs.
Bourgeois in U.S. Pat. No. 6,026,326 describes primarily enhancements to the Familoni invention for treating gastric rhythm abnormalities.
The present invention envisions an implantable neuromuscular stimulator with multiple (two or more) outputs producing sequential, prolonged pulses of 0.5 msec to 5 msec. Sequential and appropriate activation of the GI tract is produced by electrical stimulation pulses that are timed at intervals consistent with normal patterns of GI tract function for the specific spacing of the electrodes. In addition to creating gastrointestinal tract function similar to normal, this process has the potential to reeducate the GI tract to function near to normal patterns without stimulation. There is also good evidence that acid reflux can eventually cause esophageal cancer (after Barrett""s esophagus, a complication of GERD that frequently leads to esophageal cancer) and the presence of reflux seems to interfere with the normal pattern of GI function all the way to the bowel.
Important areas for electrode placement include the upper esophagus, lower esophageal sphincter, stomach, duodenum, small intestine (optional) and the large bowel (colonxe2x80x94optional).
The present invention is a neuromuscular stimulator for sequential responsive stimulation to restore normal GI function. The most likely scenario for treating acid reflux will involve electrodes placed at the esophageal sphincter and stomach wall. When initiated, the stimulator will close the esophageal sphincter and start a timer. At the end of a preset time (e.g. 0.5-2 hours) the stomach electrodes will be energized to empty the stomach. At the end of a follow on period of time, at which the stomach should now be empty, the device will turn off all stimulation and be ready for the next sequence. Stimulation may be patient initiated from external device. This device may include buttons for initiating the sequence of stimulation and buttons for temporary suspension of the program to allow snacking.
For specific patterns of electrical activity associated with eating a meal the sequence can begin automatically when no food has passed through the esophagus for a preset period of time (e.g. 10 min). Eating or drinking is easily characterized by a higher frequency of swallowing than is typical of just normal saliva swallowing. After the meal is over and the sequence has been started, if additional food or drink or just normal saliva swallowing is detected by signals picked up by an electrode on the esophagus, the system may go into suspend mode for a specified period of time (e.g. 1 to 10 sec).
The stimulator would typically involve two to four electrodes acting as sensing and/or stimulating electrodes.
The control module will have data recording capabilities and a physician""s workstation similar to that described by Fischell et. al in U.S. Pat. No. 6,016,449. The physician""s workstation would have the capability to retrieve the data recorded by the control module and to program the specific functionality of the control module including parameters for stimulation and detection of gastrointestinal tract function.
It is also envisioned that additional types of sensors other than electrodes may be used for identifying motion or actions by parts of the gastrointestinal tract. These additional sensors could include temperature sensors, motion sensors (accelerometers) and pressure sensors to sense pressure within a gastrointestinal tract structure or pressure changes caused by expansion or contraction of a gastrointestinal tract structure.
Applying electrical stimulation to the gastrointestinal tract can have the effect of suppressing appetite but more important still is the potential of electrical stimulation of the gastrointestinal tract to produce xe2x80x9cintestinal hurryxe2x80x9d where the food is passed through the gastrointestinal tract more quickly than normal so as to reduce the body""s absorption of nutrients. Gastrointestinal tract hurry can be produced by stimulation of the stomach and/or small intestine. The closed loop system envisioned would detect food being swallowed and/or stomach activity and responsively stimulate the gastrointestinal tract to increase the speed of passage of food through the small intestine. This technique should be less invasive than current surgical methods to reduce nutrient uptake and if not successful, surgery can still be performed.
Gastrointestinal tract stimulation according to the invention may be continuous, intermittent, or responsive to patient initiation or gastrointestinal tract activity detection.
Thus it is an object of the invention to have a system for restoration of normal gastrointestinal tract function by sequential stimulation signals applied to two or more electrodes placed on or near the structures of the gastrointestinal tract.
Another object of this invention is to use the sensing of gastrointestinal tract activity to initiate responsive stimulation to the gastrointestinal tract.
Another object of this invention is to use sensing of gastrointestinal tract activity to set the timing of sequential stimulation of the gastrointestinal tract.
Still another object of this invention is to have a system of electrodes connected by leads to a control module, the entire system being placed under the skin and being essentially contained within the abdomen.
Still another object of this system is to have data recording capability within the control module.
Yet another object of the present invention is to have external equipment including a patient initiating device.
Yet another object of the present invention is to have external equipment including a physician""s workstation for reading out recorded data and programming the gastrointestinal tract stimulator.
Still another object of the system is to sense sphincter contraction or relaxation in order to activate electrical stimulation of the sphincter.
Still another object of the system is to sense sphincter contraction and augment or assist this with electrical stimulation and/or trigger assistance from an artificial sphincter. This has applications for any sphincter system (e.g. gastroesophageal, pyloric, anal, bladder or urethra).
Yet another object of the present invention is to stimulate the stomach and/or small intestine to produce gastrointestinal hurry where the speed of the passage of food through the gastrointestinal tract is increased so as to reduce the absorption of nutrients as a means to achieve weight loss for obese patients.
These and other objects and advantages of this invention will become apparent to a person of ordinary skill in this art upon careful reading of the detailed description of this invention including the drawings as presented herein.